building a "Buffer Sampler"

[amptramp]

You can get rotary switches where one deck of the switch connects everything together but the selected position and the connection goes to ground to avoid introducing noise to any of the inputs.  Stray inputs to a deselected buffer can modulate the power supply current demand which can then show up as a voltage modulation of the power supply.  A single transistor or FET buffer has almost no power supply rejection.  An op amp may have some power supply rejection but unless you ground the inputs of the other buffers, you may get response up to AM radio frequencies on a FET buffer which may get demodulated and show up as an audio modulation of the power supply.

Ground the input to any stage you are not using.

[mg.audio]

You can get rotary switches where one deck of the switch connects everything together but the selected position and the connection goes to ground to avoid introducing noise to any of the inputs...

This was another concern of mine and I've been racking my brain trying to figure out how to do this. So, I guess I need a special switch. I'm not sure what term to search for, can you point me to a source that has this type of switch?

Also, will I need a second one of these special decks in the switch for hanging capacitor leads on the output side?

Here's the schematic I have so far:


Edit: I should mention the opamps in that schematic are intended to be sockets, so that I can compare single and dual opamps.

[amptramp]

I have a number of radios with shortwave bands where the selected RF, mixer and oscillator coils go to a terminal on one side of the switch deck and the other side is a shorting bar that shorts all the unselected coils and takes them to ground to prevent spurious responses.  These may not be a common item any more and would be seen more in surplus shops, but they did exist and someone may still be making them.  It is possible to simulate this if you have one deck for each buffer by tying the input to pin 1 of the first deck, pin 2 of the second and so on and taking all other pins to ground.

[duck_arse]

an old stereo hi-fi amp may have a 3 or 4 way switch with a shorting wafer and a non-shorting wafer.

[Kipper4]

"Edit: I should mention the opamps in that schematic are intended to be sockets, so that I can compare single and dual opamps."

singles and duals have different pinouts.

[mg.audio]

"Edit: I should mention the opamps in that schematic are intended to be sockets, so that I can compare single and dual opamps."

singles and duals have different pinouts.

Yes, that's why there are two opamp sockets for each opamp buffer. One for singles, the other for duals.